Provide better defaults or expose config for h2 server received header frames max size

[alpeb]

What problem are you trying to solve?

Ref #14046

Various users are reporting 431 Request header fields too large errors when issuing requests to meshed targets.

How should the problem be solved?

We need to determine first the circumstances under which this happens. Once that's clearer we can either increase the default for max_header_list_size, or expose a config for it.

Any alternatives you've considered?

Currently the workaround is to use additionalEnv, which is just an escape hatch:

proxy:
  additionalEnv:
  - name: LINKERD2_PROXY_OUTBOUND_SERVER_HTTP2_MAX_HEADER_LIST_SIZE
    value: xxx
  - name: LINKERD2_PROXY_INBOUND_SERVER_HTTP2_MAX_HEADER_LIST_SIZE
    value: xxx

How would users interact with this feature?

No response

Would you like to work on this feature?

None